There were 2 styles of valve adjusment methods on the 2.0 FIAT Dino and Ferrari Dino. The early style requires the removal of the camshaft to adjust the valves I don't have this style but I can easily imagine how frustrating it must be. Check the clearance, remove the camshaft, swap shims, reinstall the camshaft and check the clearance gap again. If you were off on your math, redo the above steps. FIAT changed to what is called the later style and used the same method as the 124 commonly known as the FIAT Spider, the later style is much easier. The later style was also used on the Ferrari Dino 246 and of course FIAT Dino 2.4

FIAT Dino Valve Adjustment
The EARLY style, you can see under the cup and between the valve keepers a shim, this is the shim you replace to adjust valves. You have to remove the camshaft to change that shim.		The later style, here you can see the cup on top of the valve has a cutout and inside that cutout is the shim, this does not require removal of the camshaft.

Consulting your manual, first write in the factory-recommended clearances in the correct clearance column. Next, following the procedure in the service manual, measure the clearance between the heel of each cam lobe and its tappet, and record your findings in the current clearance column. Then compare these measurements with factory specs and record the variance in the +/- column. Now, measure the thickness of the existing shim with your micrometer, recording this in the current shim column. Add or subtract the value in the +/- column to (or from) the current shim size. The resulting figure is the shim needed to restore proper clearance. Round up or down to the nearest size. Alfa shims are graduated in .025mm steps, Fiat shims in .05mm steps. If a valve is split evenly between two sizes, round downward (it's safer to have a valve a bit too loose than too tight).

An EXAMPLE of how to do the math !

This is a early style picture but the checking and setting is exactly the same, its just math :)